#include<iostream>
#include <openssl/md5.h>

int main()
{
    const unsigned char *key = nullptr;
    int len = 3;

    unsigned char* results = nullptr;

    MD5_CTX my_md5;

    MD5_Init(&my_md5);
    MD5_Update(&my_md5, (const unsigned char *)key, len);
    MD5_Final(results, &my_md5);

    return 0;
}